Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
  • D21H11/16—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only modified by a particular after-treatment
  • D21H11/20—Chemically or biochemically modified fibres
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/1026—Other features in bleaching processes
  • D21C9/1042—Use of chelating agents
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/001—Modification of pulp properties
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/16—Bleaching ; Apparatus therefor with per compounds
  • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides

Definitions

• This invention relates generally to pulp and paper making, and more particularly to brightness enhancing for peroxide and hydrosulfite bleaching of pulp.
• 4 wt. % lignin is normally left in hardwood chemical pulps and from about 4 wt. % to about
• 10 wt. % lignin is normally left in softwood chemical pulps after the cook or digestion.
• the lignin is subsequently removed by bleaching in separate pulp mill operations if completely delignified and whitened pulps are to be produced.
• the dominant chemical wood pulping process is the kraft ("kraft" means strength in German) or sulfate process.
• kraft means strength in German
• sulfate the alkaline pulping liquor or digesting solution contains about a 3 to 1 ratio of sodium hydroxide and sodium sulfide. A stronger pulp is obtained when sodium sulfide is used in combination with sodium hydroxide. This is to be compared with pulp obtained when sodium hydroxide is used alone, as it was in the original soda process.
• the wood is delignified (pulped) with a solution of sodium hydroxide and the addition of sodium sulfide is beneficial for pulping as well.
• Key advantages of the kraft process is its great adaptability of pulping many different species of wood and yielding pulps that may be used for a variety of applications.
• Another type of chemical pulping is the "sulfite process".
• the sulfite process has several advantages over the kraft process. These advantages include improved yield (45-55%), lower cost cooking chemicals, higher brightness pulps and more easily bleached pulps.
• the sulfite method also has two distinct disadvantages: only a limited number of species can be pulped and the pulps produced are distinctly weaker than those made using the kraft or sulfate process.
• the first step in the mechanical pulping process is the grinding or refining of wood.
• the Stone Groundwood (SGW) process involves making pulp by pressing logs and chips against an abrasive rotating surface. Many years ago the grinding surface used was an actual stone. In current practice specifically designed "artificial pulp stones" are available for the grinding.
• a Pressurized GroundWood (PGW) process is where the grinding operation is completely pressurized.
• RMP Refiner Mechanical Pulp
• TMP Thermo Mechanical Pulping
• TRMP Mechanical Pulping
• CMP ChemiMechanical Pulping
• SCMP SemiChemical Mechanical Pulping
• CMP ChemiThermoMechanical Pulping
• Pulp brightness is a measurement of the ability of a sample to reflect monochromatic (457 nm) light as compared to a known standard, using magnesium oxide (MgO). Since cellulose and hemicellulose are white, they do not contribute to pulp color. It is generally agreed that the lignin left in the pulp after pulping is responsible for the color the pulp. This unbleached pulp has an appearance similar to brown grocery bags.
• the chromophores are believed to be quinone-like materials formed from the lignin's phenolic groups through an oxidative mechanism. Additionally, heavy metal ions, especially iron and copper, can form colored complexes with the phenolic groups. There are generally two approaches to removing color.
• the bleaching of pulp is the standard method of removing color from pulp. It is current state of the art technology for all chemical and mechanical pulps to be bleached.
• chemical pulp the bleaching of pulp and the subsequent delignification of pulp is usually performed in several chemical stages, with each stage being referred to by a letter designation. Note, that although all pulps are bleached, only chemical pulps are delignified using oxygen treatment. The following table briefly describes the most common stages in a "typical" chemical bleaching process.
• auxiliary chemicals include sodium silicate for stability and chelation, sodium hydroxide for alkalinity, chelating agents such as ethylenediaminetetraacetic acid or its known salts (EDTA) and diethylenetriamine pentaacetic acid or its known salts (DTP A) for control of transition metals, and magnesium sulfate for cellulose stability.
• EDTA ethylenediaminetetraacetic acid or its known salts
• DTP A diethylenetriamine pentaacetic acid or its known salts
• magnesium sulfate for cellulose stability.
• the known chelants used in hydrogen peroxide bleaching (1) are usually selective in regards of the target transition metal ions (e.g., removing manganese but not iron or vice versa); (2) must be applied in substantial quantities to achieve a noticeable effect; and (3) require washing out complexes formed during the treatment.
• Selectivity as it applies in oxygen delignification, is defined as the ratio of the change in delignification (kappa number that characterizes lignin removal; the lower the better) divided by the change in viscosity (that characterizes carbohydrate depolymerization, the higher the better).
• the commonly used chemical for increasing the selectivity of oxygen delignification is magnesium sulfate.
• This patent describes and claims a method for making a Chemical or Mechanical pulp comprising the steps of digesting wood chips in the digester(Chemical) or grinding wood chips using mechanical grinding techniques (Mechanical) to create unbleached pulp and then bleaching the pulp and optionally subjecting the pulp to pressurized oxygen delignification(only with Chemical pulps); where the improvement comprises treating the pulp with from about 0.002 weight % to about 0.02 weight % of an organic sulfide chelating agent before or during bleaching, or before optional oxygen delignification of the pulp. It would be desirable to identify additional or alternative compounds capable of brightness enhancement during bleaching of mechanical and chemical pulp.
• the first aspect of the instant claimed invention is, in a method for making chemical pulp comprising the steps of digesting wood chips in the digester to create unbleached pulp and then bleaching the pulp using peroxide as the bleaching agent, the improvement comprising treating the pulp with from about 0.01 weight % to about 5 weight % of a Mixture comprising a) from about 40 weight % to about 60 weight % water; b) from about 20 weight % to about 95 weight % diethylenetriaminepentakis(methyl)phosphonic acid or its known salts; c) from about 5 weight % to about 50 weight % polyacrylic acid or its known salts; and optionally d) from about 1 weight % to about 20 weight % of one or more inert compounds; wherein said Mixture is added before or during bleaching.
• the second aspect of the instant claimed invention is in a method for making mechanical pulp comprising the steps of grinding or refining wood to create unbleached pulp and then bleaching the pulp; using peroxide or hydrosulfite as the bleaching agents, the improvement comprising treating the pulp with from about 0.01 weight % to about 5 weight % of a Mixture comprising a) from about 40 weight % to about 60 weight % water; b) from about 20 weight % to about 95 weight % diethylenetriaminepentakis(methyl)phosphonic acid or its known salts; c) from about 5 weight % to about 50 weight % polyacrylic acid or its known salts; and optionally d) from about 1 weight % to about 20 weight % of one or more inert compounds; wherein said Mixture is added before or during bleaching.
• the third aspect of the instant claimed invention is a composition of matter comprising a) from about 40 weight % to about 60 weight % water; b) from about 20 weight % to about 95 weight % diethylenetriaminepentakis(methyl)phosphonic acid or its known salts; c) from about 5 weight % to about 50 weight % polyacrylic acid or its known salts; and optionally d) from about 1 weight % to about 20 weight % of one or more inert compounds.
• Aldrich refers to Aldrich, P.O. Box 2060, Milwaukee, WI 53201.
• AMP refers to aminotris(methylenephosphonic acid) or its known salts.
• CAS Registry Number is the Chemical Abstracts Services Registry Number.
• CTMP ChemiThermoMechanical Pulping.
• DTPA diethylenetriaminepentaacetic acid or its known salts.
• DTMPA diethylenetriaminepentakis(methyl)phosphonic acid or its known salts.
• EDTA refers to ethylenediaminetetraacetic acid or its known salts.
• MgO refers to magnesium oxide.
• Nalco refers to Nalco Company, 1601 W. Diehl Road, Naperville, IL 60563, (630) 305-1000.
• PA refers to polyacrylic acid or its known salts.
• PGW Pressurized Groundwood pulp.
• RMP refers to Refiner Mechanical Pulp.
• SCMP SemiChemical Mechanical Pulping.
• SGW refers to Stone GroundWood pulp.
• TMP refers to Thermo Mechanical Pulping.
• TRMP refers to Thermo Refiner Mechanical Pulping.
• Weight % means weight of active ingredient per weight of dry pulp.
• the first aspect of the instant claimed invention is, in a method for making chemical pulp comprising the steps of digesting wood chips in the digester to create unbleached pulp and then bleaching the pulp using peroxide as the bleaching agent, the improvement comprising treating the pulp with from about 0.01 weight % to about 5 weight % of a Mixture comprising a) from about 40 weight % to about 60 weight % water; b) from about 20 weight % to about 95 weight % diethylenetriaminepentakis(methyl)phosphonic acid or its known salts; c) from about 5 weight % to about 50 weight % polyacrylic acid or its known salts; and optionally d) from about 1 weight % to about 20 weight % of one or more inert compounds; wherein said Mixture is added before or during bleaching.
• DTMPA Diethylenetriaminepentakis(methyl)phosphonic acid
• the instant claimed invention is the discovery that there is a synergism between DTMPA and polyacrylic acid allowing for a certain portion of the DTMPA to be replaced by polyacrylic acid with a certain amount of base being used to adjust the pH of the Mixture and the resulting Mixture can function as well as DTMPA functions by itself. This is an extremely valuable discovery because polyacrylic acid is much less expensive than DTMPA.
• DTMPA is known in the art and can be obtained through known chemical supply companies.
• the preferred salt of DTMPA for use in the Mixture of the instant claimed invention is the sodium salt when a sodium base, such as sodium hydroxide, is used and it is the potassium salt when a potassium base, such as potassium hydroxide, is used.
• Polyacrylic acid is a known chemical and can be obtained through known chemical supply houses.
• the preferred salt of polyacrylic acid is sodium polyacrylate when a sodium base, such as sodium hydroxide, is used and it is potassium polyacrylate when a potassium base, such as potassium hydroxide, is used.
• One product method to make the Mixture of the instant claimed invention is as follows: blend DTMPA (55.9% as a raw material containing 47% DTMPA) and polyacrylic acid or its known salts (24.5% as a raw material containing 46% polyacrylic acid or its known salts), and any commercially available base, such as sodium hydroxide, potassium hydroxide, calcium chloride and the like.
• the preferred base is sodium hydroxide(19.6% as a raw material containing 50% NaOH).
• the resulting product is a mildly acidic, water-based product Mixture comprising a) from about 40 weight % to about 60 weight % water; b) from about 20 weight % to about 95 weight % diethylenetriaminepentakis(methyl)phosphonic acid or its known salts; c) from about 5 weight % to about 50 weight % polyacrylic acid or its known salts; and optionally d) from about 1 weight % to about 20 weight % of one or more inert compounds.
• the preferred formula of the Mixture comprising a) about 50 weight % water; b) about 29 weight % diethylenetriaminepentakis(methyl)phosphonic acid or its known salts; c) about 14 weight % polyacrylic acid or its known salts; and optionally d) about 7 weight % of one or more inert compounds.
• the Mixture may be prepared as described by a person of ordinary skill in the art of chemistry. When sodium hydroxide is used as a base, the inert compounds are typically selected from the group consisting of sodium chloride, sodium sulfate and ammonium sodium sulfate.
• the inert compounds are typically selected from the group consisting of potassium chloride, potassium sulfate and ammonium potassium sulfate.
• the preferred option for the Mixture applied is to use sufficient base to render the Mixture as close to neutral as possible in the pulp to which it is applied. If the pH is too low or too high, then the pH of the bleach liquor may be affected, thus reducing brightness. A neutral product is also preferred to lessen the possibility that the product itself could cause or contribute to corrosion in the metal equipment used in the pulp process.
• the inert compounds present in the Mixture are typically salts and sulfates, either present in small quantities in the original DTMPA or its known salts or in the polyacrylic acid and its known salts or in the base used.
• typically the inert materials present include sodium chloride, sodium sulfate and ammonium sulfate.
• the inert compounds present in the Mixture do not contribute to the activity of the Mixture for this application. It has been found that when this Mixture is added to chemical pulp that it works to either maintain or slightly enhance the brightness of the pulp, if nothing else is changed about the chemicals added to the pulp. Or the Mixture can be used to maintain the brightness of the pulp while amount(s) of other chemicals typically added are reduced.
• This Mixture also works to either enhance or maintain the brightness of recycled pulp, wherein the recycled pulp comprises chemical pulp or a blend of chemical and mechanical pulp.
• the amount of bleaching chemical(s), such as hydrogen peroxide can be replaced by the Mixture. Replacing some of the bleaching chemical(s), with the Mixture, allows a pulp and paper company to reduce production costs while achieving the target brightness in the chemical pulp.
• the amount of magnesium added to the chemical pulp can be reduced, when the Mixture is added to the chemical pulp, because use of the Mixture has been found to improve viscosity similarly to magnesium, but at much lower dose.
• Delignification is also known as "lignin removal" and is characterized by the kappa number of the pulp.
• the kappa number of the pulp is the volume, usually reported in ml of 0.1 N potassium permanganate solution consumed by one gram of moisture-free pulp under the conditions specified in TAPPI Method T236om-99.
• the kappa number is linearly proportional to the amount of residual lignin in the pulp.
• the Pulp viscosity is determined by the capillary viscometer method, TAPPI Method T23om-99. It has been found that when the Mixture is added to a Chemical pulp prior to pressurized oxygen delignification, that the delignification is enhanced.
• the same Mixture that is useful in improving brightness is also useful in enhancing oxygen delignification. Relatively speaking the same amount of the Mixture is used to enhance oxygen delignification as is used to enhance brightness.
• a preferred embodiment of the instant claimed invention is that amount of DTMPA in the Mixture that yields the same brightness value as does the use of DTMPA by itself.
• the Mixture has been found to work effectively both in peroxide, including Eop process, bleaching of Chemical pulp and in peroxide and hydrosulfite bleaching of Mechanical pulp.
• the Mixture can also be used to enhance oxygen delignification.
• the Mixture is recommended to be applied either in pre-treatment or directly into bleach liquor for maximum performance.
• the amount of Mixture applied is from about 0.01 weight % to about 5 weight % of the pulp.
• the preferred amount of Mixture is from about 0.10 weight % to about 1 weight %.
• the most preferred amount of Mixture is about 0.20 weight %.
• the preferred embodiment of the instant claimed invention is having the minimal amount of DTMPA used in the Mixture while still achieving the same or an acceptable level of brightness in the pulp. As has been previously discussed, with some pulps, it has been found that by using the Mixture, and not changing the amounts or type of any of the other additives to the pulp that the brightness value of the chemical pulp is increased.
• the second aspect of the instant claimed invention is in a method for making Mechanical pulp comprising the steps of grinding or refining wood to create unbleached pulp and then bleaching the pulp; using peroxide or hydrosulfite as the bleaching agents, the improvement comprising treating the pulp with from about 0.01 weight % to about 5 weight % of a Mixture comprising a) from about 40 weight % to about 60 weight % water; b) from about 20 weight % to about 95 weight % diethylenetriaminepentakis(methyI)phosphonic acid or its known salts; c) from about 5 weight % to about 50 weight % polyacrylic acid or its known salts; and optionally d) from about 1 weight % to about 20 weight % of one or more inert compounds; wherein said Mixture is added before or during bleaching.
• the Mechanical pulp can be one of several types including SGW and PGW pulp, RMP, TMP and TRMP.
• the Mixture suitable for use in this second aspect of the instant claimed invention are the same as those listed for use in the first aspect of the instant claimed invention.
• the Mixture is recommended to be applied either in pre-treatment or directly into bleach liquor for maximum performance.
• the amount of Mixture applied is from about 0.01 weight % to about 5 weight % of the pulp.
• the preferred amount of Mixture is from about 0.10 weight % to about 1 weight %.
• the most preferred amount of Mixture is about 0.2 weight %.
• the preferred embodiment of the instant claimed invention is having the minimal amount of DTMPA used in the Mixture while still achieving the same or an acceptable level of brightness in the pulp.
• This Mixture also works when added to mechanical pulp, wherein the total amount of sodium silicate present in the pulp is reduced. It has been found that even with the total amount of sodium silicate reduced in the mechanical pulp, use of this Mixture allows the target brightness for the mechanical pulp to be achieved.
• This Mixture also works when added to mechanical pulp, wherein the total amount of both sodium silicate and peroxide present in the pulp is reduced. It has been found that even with the total amount of both sodium silicate and peroxide reduced in the mechanical pulp, use of this Mixture allows the target brightness for the mechanical pulp to be achieved.
• the invention has been described with reference to the preferred embodiment. Obvious modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
• EXAMDTMPA refers to an aqueous solution with 47% DTMPA in the mixture
• EXAMPAA refers to an aqueous solution with 46% polyacrylic acid.
• sufficient base with the base being sodium hydroxide as an aqueous 50% solution of NaOH was added to achieve appropriate pH for the Mixture being tested. All percentages in these examples are given on a weight percent dry pulp basis.
• Brightness is a term used to describe the whiteness of pulp on a scale: from 0%, meaning absolute black, to 100%o, relative to MgO standard, which has an absolute brightness of ca. 96%; by the reflectance of blue light (457 mm) from the paper produced from the pulp.
• DTPA DTPA plus undefined phosphonates.
• PREFMIX refers to a Mixture with the following composition: a) about 50 weight % water; b) about 29 weight % sodium diethylenetriaminepenta(methylene phosphonate); c) about 14 weight % sodium acrylate; d) about 7 weight % of one or more inert compounds, wherein the inert compounds are sodium chloride, ammonium sodium sulfate and sodium sulfate.
• Pulp Pulp Mill Blue, TMP, 4.5%. Bleaching: 70°C, 1 hr, 10% consistency,
• Pulp Pulp Mill Red, PGW, 8.2%. Bleaching: 70°C, 1 hr, 10% consistency,
• Bleaching 65°C, 1 hr, 10% consistency, 1.5% NaOH, 2% H 2 O 2 .
• Test 4 Pulp: Pulp Mill Orange, PGW, 7.9%. Pretreatment (samples 1-5 only): 15 min, 50 °C, 2% consistency, tap water. Bleaching: 70°C, 1 hr, 10% consistency, 2% NaOH, 2.5% H 2 O 2 .
• Pulp Pulp Mill Brown, kraft hardwood pulp (aspen), 35.7%. Bleaching: 85°C,
• Pulp Pulp Mill Brown, kraft hardwood pulp (maple), 34.5%. Bleaching: 85°C,
• Pulp Pulp Mill Lime Green, kraft 16.3%. DI water was used to adjust consistency. Bleaching: 75°C, 1 hr 15 min, 10% consistency, 1.8% NaOH, 0.75%

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• Wood Science & Technology (AREA)
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• Biochemistry (AREA)
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• Compositions Of Macromolecular Compounds (AREA)

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• 2004
  • 2004-03-31 US US10/814,969 patent/US7351764B2/en not_active Expired - Fee Related
• 2005
  • 2005-02-25 BR BRPI0509510-7A patent/BRPI0509510A/pt not_active IP Right Cessation
  • 2005-02-25 CA CA002562026A patent/CA2562026A1/en not_active Abandoned
  • 2005-02-25 EP EP05723836A patent/EP1730227A4/de not_active Withdrawn
  • 2005-02-25 WO PCT/US2005/006143 patent/WO2005103135A1/en active Application Filing
  • 2005-02-25 JP JP2007506177A patent/JP2007530818A/ja active Pending
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